In the well-known gas turbines of the compressor-combustor type, the turbine blades are remote from the combustor and large additional quantities of compressed air are fed to a secondary zone of the combustion chamber to combine with the hot, expanding combustion gases, prior to such gases reaching the turbine blades, to reduce the gas temperature to a value that will not cause damage to the turbine blades, see for example, Gas Turbine Power, Second Edition, 1958, G. M. Dusinberre and J. C. Lester; The Gas Turbine Engine, 1975, Jan P. Norbye; Automotive Gas Turbines, Second Edition, 1969, Bill Carroll; and Gas Turbine Engineering Handbook, First Edition, 1966, John W. Sawyer.
Applicant's related patent application Ser. No. 879,969, filed Feb. 21, 1978, which is incorporated by reference herein in its entirety, discloses and describes a Lowther Gas Turbine which comprises a gas turbine method and apparatus using an intermittent burn operating cycle referred to as a burn-cool cycle, comprising a burn phase followed by a cool phase. This cycle includes: (1) feeding fuel to the burn chamber and burning it during the burn phase of the cycle, whereby the temperature of the chamber and turbine rises during the burn phase, and (2) cutting off most or all of the flow of fuel to the burn chamber during the cool phase whereby the temperature of the chamber and turbine falls. The air-to-fuel ratio during the burn phase is always the same, providing a high combustion temperature and high efficiency. The part-load efficiency loss problem of the prior art is eliminated by the related invention. In the prior art, under part-load, the air-to-fuel ratio was increased, thus resulting in a reduced burning temperature and reduced efficiency. The combustion temperature is much higher than the temperature that the structure is allowed to reach because of the intermittent burn cycle and the cool down phase, thus eliminating the need for high temperature materials. In addition, lower amounts of a source of oxygen, such as air, are needed as compared to the prior art gas turbine. For example, the Lowther Gas Turbine of the related invention uses about six times smaller volume of gas than does the well-known Chrysler automobile gas turbine.
The Lowther Gas Turbine also includes means for preventing the shaft speed from decreasing during the cool phase. This is accomplished by a flywheel action using, for example, a mechanical flywheel, an electric flywheel or a chemical flywheel. The related invention also includes the controlling of the length of at least one of the burn and cool phases to control the power output of the turbine. For example, if it is desired to increase power, the length of the burn phase can be increased, or the length of the cool phase can be decreased or both.
The Lowther Gas Turbine of the related invention also involves the use of different amounts and pressures of air during the cool phase than are used during the burn phase. Another aspect of that invention is the use of water injection during the cool phase to improve cooling. The water can be recovered in a condensor and recycled.
Yet another aspect of the Lowther Gas Turbine includes the use of two different fuels, one, for example, can be used in the burn phase and the other in the cool phase. In another embodiment of that invention the shaft is connected to an electric generator and to a traction motor. A gear box, electric generator and battery can also be used in various combinations along with water injection. In addition, a heat exchanger can be used to pre-heat the compressed gas prior to its being fed into the combustion chamber.
The related invention also includes embodiments employing a free turbine. Combined cycle embodiments of the related invention include the use of a second working fluid operating with either an open or closed cycle and with a second working fluid operating to drive a turbine.
Also, the Lowther Gas Turbine includes embodiments using plural turbines and plural burn chambers in which the intermittent cycle is employed in each burn chamber. There is a staggered burn cycle from one burn chamber to the next which, in the preferred embodiment, is a uniform staggered burn cycle. A preferred air-to-fuel ratio is in the range of 14.7:1 to 35:1. A preferred burn phase to cool phase is 90% to 10% in length of time of the respective phases.
An example of the intermittent burn-cool cycle of the Lowther Gas Turbine also is disclosed in applicant's related copending patent application Ser. No. 889,851, filed Mar. 24, 1978, wherein the rate of cooling of the turbine blades is enhanced by spraying fuel oil directly on the convex surface of the blades thereby shortening the cooling period. Ser. No. 889,851 is incorporated herein by reference in its entirety.
FIG. 17 of the above-identified patent application Ser. No. 879,969, shows an example of a chemical flywheel. According to the invention disclosed in that patent application, a cryogenic material, such as dry ice, liquid air, or liquid oxygen is vaporized and passed through the gas turbine system during the cooling period. The cryogenic material there serves two purposes: it expands and drives the turbine 12, of said FIG. 17, and it cools all the exposed parts that were heated during the burn phase of the burn-cool cycle described in that patent application.
U.S. Pat. No. 3,775,976, issued Dec. 4, 1973, describes the use of oxygen derived from a cryogenic source as an oxidant for a turbine engine in a thermal power system operated at near atmospheric pressures for a submersible. The patent describes methods and means for operation of the power system in either a closed or an open-circuit mode. Some features of the methods and means for operation of the turbine as described in the patent generally can be utilized in combination with applicant's Lowther Gas Turbine and with embodiments of applicant's present invention, as will be understood by those skilled in the art.